1. FIELD OF THE INVENTION
The present invention relates generally to laminated ceramic armor materials and more specifically, to an improved ballistic armor laminate having a novel spall shield comprising a plasticized resin material such as that used as the plasticized interlayer in conventional laminated safety glass.
2. PRIOR ART
Conventional ceramic armor materials typically employ a laminated structure comprising a layer of ceramic material such as boron carbide and a layer of reinforced glass fabric such as Kevlar. The ceramic layer typically faces the expected incoming projectiles and is typically covered with what is called a spall shield, a thin, flexible, rubberized layer or sheet which is provided as the outer layer facing the incoming projectiles. This sheet may also be of ballistic nylon cloth or felt or resin impregnated glass fabric and is designed to prevent fragmentation of ceramic particles subsequent to the impact by the projectile. This sheet is typically adhered to the ceramic surface by some form of adhesive. One of the problems associated with using a nylon adhered spall shield is that it adds a considerable amount of weight to the ceramic armor. Another problem is the likelihood of a rip or tear which would allow fragments to be propelled by impact without restraint.
The concept of utilizing a laminated configuration of ceramic reinforced with a layer of glass fabric as a ballistic armor material is old in the art. By way of example, the patent to Cook (U.S. Pat. No. 3,516,898) relates to hard face plastic armor comprising a laminated structure having the combination of a facing layer made from an extremely hard material, a reinforced plastic substrata layer and flexible bonding means between the facing layer and the substrata layer wherein the facing layer is segmented into sections so that the concentrated energy of the projectile can be locally absorbed without fracture and loss of the surrounding facing. The use of a conventional spall shield comprising a thin, flexible, rubberized layer or sheet which may also be a ballistic nylon cloth and the like, is also disclosed in this patent. The patent to Triebel et al (U.S. Pat. No. 4,125,669) relates to a bullet-proof laminated safety glass which is formed of a silicate glass pane of at least 6 millimeters in thickness or an acrylic glass pane of at least 12 millimeters in thickness and a polycarbonate pane of at least 11/2 millimeters in thickness.
None of the aforementioned patents discloses a combination of materials comprising a spall shield of a plasticized resin material such as that used as the plasticized interlayer of a laminated safety glass. Unfortunately, conventional spall shields such as those employing nylon adhered to the outer layer of ceramic material, add a considerable amount of weight to the ceramic armor. In addition, conventional spall shields present certain manufacturing complexities relating to carefully adhering the nylon material to the ceramic as a spall shield to catch fragments of the projectile as well as fragments of the ceramic that result from the impact of the projectile with the armor. Furthermore, nylon spall shields tend to be ripped or torn upon impact of a projectile and may reduce the ballistic properties of the armor combination.